It is sometimes necessary to remove one or more vertebrae, or a portion of the vertebrae, from the human spine in response to various pathologies. For example, one or more of the vertebrae may become damaged as a result of tumor growth, or may become damaged by a traumatic or other event. Removal, or excision, of a vertebra may be referred to as a vertebrectomy. Excision of a generally anterior portion, or vertebral body, of the vertebra may be referred to as a corpectomy. An implant is usually placed between the remaining vertebrae to provide structural support for the spine as a part of a corpectomy. FIG. 1 illustrates four vertebrae, V1-V4 of a typical lumbar spine and three spinal discs, D1-D3. As illustrated, V3 is a damaged vertebra and all or a part of V3 could be removed to help stabilize the spine. If removed along with spinal discs D2 and D3, an implant may be placed between vertebrae V2 and V4. Most commonly, the implant inserted between the vertebrae is designed to facilitate fusion between remaining vertebrae. Sometimes the implant is designed to replace the function of the excised vertebra and discs. All or part of more than one vertebrae may be damaged and require removal and replacement in some circumstances. It may also be clinically appropriate in some circumstances to remove only one or a part of one of the discs, D1-D3 for example, and replace the disc or a portion of the disc with an expandable implant in a fusion procedure.
Many implants are known in the art for use in a corpectomy or fusion procedure. One class of implants is sized to directly replace the vertebra or vertebrae that are being replaced. Another class of implants is inserted into the human body in a collapsed state and then expanded once properly positioned. Expandable implants may assist with restoring proper loading to the anatomy and achieving more secure fixation of the implant. Expandable implants may be advantageous because they allow for a smaller incision when properly positioning an implant. Implants that expand from a relatively small height to a relatively tall height while providing good structural strength may be more particularly advantageous to minimize incision size. Implants that included insertion and expansion mechanisms that are narrowly configured may also provide clinical advantages. Effective implants should also include a mechanism for securely locking in desired positions, and in some situations, be capable of collapsing. Implants with openings at or near their ends may also be advantageous in some embodiments because they allow for vascularization and bone growth into or through the implant.
Expandable implants may also be useful in replacing long bones or portions of appendages such as the legs and arms, or a rib or other bone that is generally longer than it is wide. Examples include, but are not limited to, a femur, tibia, fibula, humerus, radius, ulna, phalanges, clavicle, and any of the ribs.